In a wireless device, such as a mobile phone, the linearity of the amplifiers and mixers in the transceiver portion of the wireless device is important. Without sufficient linearity the received signals of interest can become distorted if they are strong or may be masked by out of band noise when they are weak. A partial solution is to pre-filter the received signal before the low noise amplifiers (LNA) in the receiver portion of the transceiver. However, in full duplex radio systems, in which the data may be simultaneously received and transmitted by the transceiver, substantial transmitter power may leak from the transmitter portion of the transceiver into the receiver portion of the receiver such that the transmission signal passing through the receiver portion of the transceiver can be millions of times stronger than the received signals of interest.
To address the full duplex issue, one conventional approach is to isolate the transmitter portion of the duplexer from the receiver portion of the duplexer to prevent the power from the transmitted signals from disrupting the receiver portion of the duplexer. Unfortunately, the most advanced duplexers and receiver filters conventionally used sometimes do not have enough isolation to compensate for the non-linearity of the LNAs and the mixers that are used in the receiver portion of the transceiver. Further such an approach may result in a degradation of the noise figure for the receiver portion of the transceiver.
To further address this issue, tradeoffs can be made when designing the LNA used in the receiver. For instance, tradeoffs can be made when selecting the LNA's noise figure (NF), gain, linearity, stability and power consumption. However, certain conventional LNAs may have a poor design that does not have good linearity or stability. For instance, some conventional designs may trade off too much NF and gain to achieve better linearity.